Heh, I also solved it a few months ago and didn't get a response (though I wasn't nearly as snarky as you good sir, hat tip). I agree that they should at least send a response to every participant. Even an automated one with a more fun problem would be nice.
Hey there! Sorry for the delay in response. Rest assure we review all applicants and reach out if there is a strong match. We appreciate you taking the time and working on the challenge, hopefully you enjoyed it :)